LSM Antibody: Significance and Treatment
LSM (Liver Stiffness Measurement) is not an antibody but rather a non-invasive diagnostic technique used to assess liver fibrosis and portal hypertension, primarily through transient elastography (TE) and other elastography methods.
What is LSM?
- LSM refers to Liver Stiffness Measurement, a non-invasive diagnostic technique used to evaluate liver disease severity, particularly fibrosis staging and portal hypertension 1
- The most common method for LSM is vibration-controlled transient elastography (VCTE), often referred to simply as transient elastography (TE) 1
- Other elastography techniques include point shear wave elastography (pSWE), two-dimensional shear wave elastography (2D-SWE), and magnetic resonance elastography (MRE) 1
Clinical Significance of LSM
Diagnosis of Advanced Liver Disease
- LSM by TE is strongly recommended for ruling out and diagnosing compensated advanced chronic liver disease (cACLD) using the following cut-offs: <8-10 kPa to rule-out; >12-15 kPa to rule-in 1
- In patients with Primary Biliary Cholangitis (PBC), LSM by TE is the best surrogate marker for ruling in severe fibrosis/cACLD using a cut-off of 10 kPa 1, 2
- In patients with Primary Sclerosing Cholangitis (PSC), LSM by TE above 9.5 kPa can support the diagnosis of advanced fibrosis in compensated patients with normal bilirubin and without high-grade stenosis 1
Portal Hypertension Assessment
- LSM by TE at a cut-off of >20-25 kPa should be used to diagnose clinically significant portal hypertension (CSPH) in patients with cACLD 1
- In patients with cACLD due to various etiologies, LSM by TE <20 kPa combined with platelet count >150 G/L (Baveno VI criteria) can rule out high-risk varices and avoid unnecessary endoscopic screening 1
- For precise assessment of portal hypertension severity beyond presence/absence of CSPH, hepatic venous pressure gradient (HVPG) remains the only validated tool and should not be substituted by non-invasive tests 1
Monitoring Disease Progression and Treatment Response
- LSM by TE can be used in patients with treated autoimmune hepatitis (AIH) to monitor disease course together with transaminases and IgG, and to stage liver fibrosis after at least 6 months of immunosuppressive therapy 1
- In patients with PBC, non-invasive discrimination of early and advanced stage disease based on biochemical parameters (albumin and bilirubin) and LSM by TE is recommended at baseline 1
- During treatment of PBC, risk stratification should be based on response assessment using risk scores and LSM by TE 1, 2
Interpretation Considerations and Limitations
- Inter-system variability should be considered when interpreting results from different elastography techniques, as values, ranges, and cut-offs are not comparable across platforms 1
- Hepatic inflammation can lead to overestimation of liver stiffness, independently from fibrosis stage 1
- In PSC patients, cholestasis related to untreated dominant biliary strictures can influence liver stiffness assessment 1
- LSM is less accurate in severe portal hypertension (HVPG values above 12 mm Hg), as higher portal pressures often depend on extrahepatic factors that LSM cannot assess 1
Follow-up Recommendations
- For patients with non-alcoholic fatty liver disease (NAFLD), it is reasonable to repeat non-invasive tests every 3 years in patients with early-stage disease and annually in those with advanced-stage disease 1
- Annual assessment using transient elastography and platelet count should be considered for monitoring patients with PBC 2
- In patients with PSC, both the ELF score and LSM by TE correlate with outcomes and should be used for risk stratification both at baseline and during follow-up 1
Important Note on Terminology Confusion
The term "LSM antibody" appears to be a misunderstanding or confusion with either:
If referring to anti-LSm antibodies, these are IgG autoantibodies to human LSm4 (hLSm4) detected in a large number of anti-Sm-positive sera from patients with SLE 3